Glaucoma is a group of diseases, frequently characterized by raised intraocular pressure (IOP), which affects the optic nerve, and is the second leading cause of blindness in the world. Currently, most glaucoma patients are initially managed with medical therapy. However, some patients still require surgical interventions to preserve their vision. When glaucoma continues to progress despite the use of medication regimes and possibly laser treatments (ALT or SLT treatments), a glaucoma filtration procedure (trabeculectomy) may be recommended. Additional surgical techniques for reducing intraocular pressure (IOP) include laser trabeculoplasty, non-penetrating filtration surgery (i.e. deep sclerectomy, viscocanalostomy), shunts, and cyclo-destructive procedures.
Deep sclerectomy, a non-penetrating or minimally invasive filtering surgery, is being proposed as a viable alternative to conventional trabeculectomy. In contrast to trabeculectomy, which is associated with significant morbidity, deep sclerectomy does not penetrate the eye, and has been shown to minimize intraoperative and postoperative complications.
In a manual non-penetrating deep sclerectomy (NPDS) procedure performed with manual surgical instruments, a deep scleral flap is first dissected and then a second scleral layer is cut out, leaving an exposed thin layer of trabecular meshwork and Descemet's membrane. Fluid percolation through the remaining tissue is the desired outcome of the procedure. Inadvertent perforation of the thin trabeculo-descemet membrane or alternatively an insufficiently deep second scleral flap, are relatively frequent complications, occurring in about 30% of the cases in the early stages of the learning curve of this procedure. In the case of perforation, the procedure may be converted to a conventional trabeculectomy; however, the high rates of perforation and a long learning curve limit the use of deep sclerectomy as a common treatment procedure. While the risk of perforation is relatively high, if the tissue is not cut deep enough, the filtration may not be effective and the intraocular pressure will not be reduced to the desired level. Since the scleral tissue needs to be dissected to more than 90% of its depth, leaving a residual intact layer of only several tens of microns, the procedure is very demanding and requires significant skills and expertise.
The following publications may be relevant to this application:
RE 37504 of U.S. Pat. No. 5,549,598U.S. Pat. No. 3,828,788U.S. Pat. No. 4,665,913May 1987L'Esperance, Jr.U.S. Pat. No. 4,907,586March 1990Bille et al.U.S. Pat. No. 4,963,142October 1990LoertscherU.S. Pat. No. 5,098,426March 1992Sklar et al.U.S. Pat. No. 5,364,390November 1994Taboada et al.U.S. Pat. No. 5,370,641December 1994O'Donnell, Jr.U.S. Pat. No. 5,520,679May 1996LinU.S. Pat. No. 5,529,076June 1996SchacharU.S. Pat. No. 5,620,435April 1997Belkin et al.U.S. Pat. No. 5,634,920June 1997HohlaU.S. Pat. No. 5,733,276March 1998BelkinU.S. Pat. No. 5,738,677April 1998Colvard et al.U.S. Pat. No. 5,782,822July 1998Telfair et al.U.S. Pat. No. 5,827,266October 1998Harel et al.U.S. Pat. No. 6,010,497January 2000Tang et al.U.S. Pat. No. 6,059,772May 2000Hsia et al.U.S. Pat. No. 6,159,202December 2000Sumiya et al.U.S. Pat. No. 6,220,247April 2001Maldonado BasU.S. Pat. No. 6,241,721June 2001Cozean et al.U.S. Pat. No. 6,258,082July 2001LinU.S. Pat. No. 6,263,879July 2001LinU.S. Pat. No. 6,540,391April 2003Lanzetta et al.U.S. Pat. No. 7,135,016U.S. 2001/0029363October 2001LinU.S. 2002/0026179February 2002TohU.S. 2005/0096639EP 0 765 648April 1997EP 0 770 370May 1997EP 1 138 290October 2001WO 01/50969July 2001WO 01/085044WO 03/041623    Assia E. I. et al. Experimental studies on non-penetrating filtration surgery using the CO2 laser. Graefes Arch Clin Exp Ophthalmol. 2007 June; 245(6):847-54    Barak, A. et al; “Anterior Capsulotomy Using CO2 Laser;” SPIE; vol. 3246; pp. 196-198; June 1998.    Assia, E. I. et al.; “Non-Penetrating Glaucoma Surgery Using the CO.sub.2 Laser: Experimental Studies in Human Cadaver Eyes;” Proceedings of SPIE; vol. 4245; pp. 228-233; June 2001.    Belkin, M. et al.; “Non-Penetrating Trabeculectomy Using the CO.sub.2 Laser in Rabbits;” Abstract No. 1419-B327; IOVS; vol. 40; No. 4; Mar. 15, 1999.    Wolbarsht, M.; “Laser Surgery: CO.sub.2 or HF;” IEEE Journal of Quantum Electronics; vol. QE-20; No. 12; pp. 1427-1432; December 1984.